Take a sharp pairing knife or a peeler and remove the brown skin of the taro root. Wash taro roots with water to remove all the dirt particles. I soak them in salted water for 5 minutes.
Once cleaned, transfer them to a colander or kitchen towel to dry up. Cut colocasia roots into juliennes or matchsticks.
Heat mustard oil in a frying pan or kadhai till it starts smoking. Reduce the heat to low.
Add cumin seeds, nigella seeds, ginger, green chilli, and asafoetida. Saute for a 20 - 30 seconds.
Add chopped taro roots, salt, red chilli powder, turmeric powder, coriander powder, and achar ka masala. Stir to combine and coat each piece with the spices.
Add water, cover, and cook the arbi fry till crisp and fully cooked. It takes 10 - 12 minutes over low heat.
Once taro roots are crisp, and cooked, garnish them with fresh coriander leaves.
Serve masala arbi fry with phulka for lunch.